This invention relates in general to wireless communication networks and applications and, in particular, to a method and system of defining locations areas within a paging area consisting of a plurality of cells utilizing the paging traffic and handoff traffic statistics related to the cells.
Without limiting the scope of the invention, its background is described in connection with defining a location area within a service area of a wireless communications network, as an example.
Present-day mobile telephony has spurred rapid technological advances in both wireless and non-wireless areas. The communications industry is a rapidly growing industry, with advances, improvements, and technological breakthroughs occurring on an almost daily basis. Many mobile communications systems, among them the European GSM-system, have already passed through several basic development phases, and system designers are now concentrating on further improvements to the systems, including system refinements and the introduction of optional services.
Most wireless communication systems currently in use are implemented as wireless communication networks. Wireless communication networks typically are composed of a group of Base Transceiver Stations (BTS), or base stations connected to a centrally located switch. This centrally located switch is commonly referred to as a Mobile Switching Center (MSC). The MSC contains definitions for Location Area, Paging Area, Satellite Paging Area, Inter-Exchange Paging Area, Service Area, Paging Extent, Paging Priority and the parameters associated with them. The MSC also contains registration parameters that are essential for the proper functioning of the paging network.
A typical wireless communications network also includes a group of interconnected MSCs, which operate in association with a gateway mobile switching center through which the wireless communications network interconnects with a conventional Public Switched Telephone Network (PSTN). In addition, at least one Home Location Register (HLR) operates within the wireless communications network. The HLR stores network subscriber information via registration, including the currently serving MSC for location of the current mobile stations within the network.
In response to an incoming call dialed to a mobile station, a signal is sent to the HLR requesting routing information through the network to the called mobile station. The HLR xe2x80x9clooks upxe2x80x9d the current location of the mobile station and contacts the currently serving MSC to pre-route the call and retrieve a temporary location directory number, which is utilized to route the call through the communications network for delivery to the mobile station. The serving MSC retrieves from a Visitor Location Register (VLR) the identification of the location area within which the called mobile station is currently located. The VLR""s function, among others, is to update its records based on the mobile station""s activity and registration and inform the mobile station""s HLR when the mobile station becomes active or inactive.
A location area is a collection of cells that covers a geographic area, or coverage area. All cells in the MSC should belong to a defined location area. If a cell is not associated with a location area, it belongs to the default location area, which is referred to as the basic location area. A collection of location areas is then commonly referred to as a paging area. Paging areas can cross MSC borders and include location areas from other MSCs. Each location area should be associated with a defined paging area, and a location area may belong to more than one paging area.
Once the MSC receives a request for paging a mobile station, it searches for that mobile station""s record in the VLR. Upon identifying the location of the mobile station using information found in the VLR, the MSC then instructs the base station(s) associated with that particular location area to page the mobile station. If no response, then the MSC might page the paging area associated with the location area. If, however, the VLR has no record for that mobile station, the location area for that mobile station is considered unknown. The MSC will then page its entire service area (all cells in that MSC) to find the mobile station. This results in a waste of system resources.
When a mobile station migrates from the coverage area of one location area to another, it registers with the MSC. In reality, there are occasions when the registration is unsuccessful due to the radio conditions (e.g., low signal strength or interference), or because the mobile is busy with other activities. Registering allows the MSC to know the location of the mobile station. In turn, the MSC uses this information to page the mobile station more efficiently. However, if the size of the location area is too small, there is a risk that the mobile station will not be found when paging in its latest known location areas, and thus paging becomes inefficient. On the other hand, if the location area is too large, then too many cells are paged unnecessarily and paging occurs in a much larger area than is necessary.
The task of grouping cells into location areas and paging areas is more an art than a science. Network engineers and wireless service providers are faced with the problem of defining location areas which may be too small given that the number of registrations increase as a mobile station moves from one location area to another. Thus, an overwhelming amount of system resources are consumed.
Presently, location areas are defined by grouping cells in a wireless communications network utilizing paging traffic statistics collected and stored by the MSC or switch equipment. Typically, counters for each cell track the number of pages and page responses. The maximum number of pages per second per location area (assuming that such information or an approximation of it is available) and the contribution of each cell to the paging are utilized in determining whether the location area can handle the amount of pages. Furthermore, natural boundaries, such as mountains and rivers are factored into defining the borders of the location areas within their respective paging area.
This prior art method, or approach, for defining and optimizing location areas within a paging area of a wireless communications network does not utilize the handoff traffic between adjacent cells. For example, if the traffic moves from one of these cells frequently to the other cell, there is a large possibility that the mobile stations move from the coverage area of one cell to the coverage area of the other cell in a very short period of time. As such, current methods are unsuitable for today""s modern wireless network. What is needed is a more efficient and accurate method and system for defining a location area in a wireless communications network utilizing existing paging traffic and handoff traffic statistics would provide numerous advantages. A method and system that reduces the number of registrations, consumes less network resources and allows for paging of a mobile station subscriber more efficiently is needed for defining location areas within the paging areas of the network.
The present invention provides a method and system for defining location areas in a wireless communications network utilizing existing paging traffic and handoff traffic statistics. With the present invention, the service provider can expect to see a decrease in the number of registrations, less network resources being consumed during the paging process and more efficient paging of a mobile station subscriber.
Accordingly, disclosed in one embodiment, is a method for use in a wireless communications network of defining location areas utilizing the paging traffic and handoff traffic statistics related to the cells in the network service area. The method comprises the steps of identifying a first cell within the paging area of the network having the highest volume of paging traffic and marking the first cell as belonging to a working location area.
Next, a second cell in the paging area is identified, the second cell being adjacent to the working location area and having the highest volume of handoff traffic with the cells in the working location area. Once the second cell has been identified, a determination is made if the combined paging traffic of the first and second cells exceeds the maximum paging capacity for a location area within the service area of the network. If the maximum paging capacity of the location area has not been exceeded, the second cell is added to the working location area.
If the second cell is added, the method further comprises the step of identifying a third cell adjacent to the working location area. The third cell is identified as as an adjacent cell to the working location area having the highest volume of handoff traffic with the cells within the working location area. The process continues until no more cells can be added to the working location area without exceeding the maximum paging capacity. At that point, the working location area becomes a defined location area within the network.
The remaining cells in the network are similarly allocated to working location areas and then to defined location areas until all cells, except for the occasional dead cell, have been allocated to a defined location area. By considering the combined paging capacity of cells which are selected for their handoff characteristics with neighboring or adjacent cells, better optimization of network resources is achieved in the wireless communications network.
Technical advantages of the present invention include a decrease in the number of registrations, less network resources being consumed during the paging process and more efficient paging of a mobile station subscriber within its location area.